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Global Experiment and Related Investigations

A. Global Experiment and Related Investigations


Validation of PD/A CRSP Pond Management Strategies

Work Plan 7, Egypt Study 1A

Bartholomew W. Green
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA

Zeinab El Nagdy and Abdel R. El Gamal
Central Laboratory for Aquaculture Research
Agricultural Research Center
Abbassa, Egypt

Abstract

The objectives of this research were to quantify tilapia yields for established Pond Dynamics/Aquaculture Collaborative Research Support Program pond nutrient input strategies under climatic, edaphic, and water quality conditions found in Egypt and to compare these results to those obtained using traditional Egyptian management practices. Five treatments, each replicated four times, were tested in 0.1-ha earthen ponds. Treatments tested were: Traditional Egyptian, Enhanced Egyptian, Feed Only, Fertilization then Feed, and Chemical Fertilization. Ponds were stocked with 20,000 Oreochromis niloticus/ha; mixed-sex fish were stocked in Egyptian treatments and sex-reversed fish in all others. Experiment duration was 145 days. Nile tilapia gross yield differed significantly among treatments and ranged from 1,278 kg/ha (chemical fertilizer treatment) to 2,877 kg/ha (fertilization then feed treatment). Wild tilapia (O. aureus, S. galilae, T. zilli) invaded all ponds and contributed 81 to 686 kg/ha to total tilapia yield treatment means. Thus, total tilapia yield ranged from 1,407 to 3,537 kg/ha and represented from 78% to 96% of gross fish yield. Gross fish yields ranged from 1,526 to 4,074 kg/ha. Tilapia yields in the Traditional Egyptian and Fertilizer then Feed treatments was significantly greater than in the Chemical Fertilizer treatment. Tilapia are marketed in Egypt by size class as follows: 1st class - 1 to 5 fish/kg; 2nd class - 6 to 12 fish/kg; 3rd class - 13 to 25 fish/kg; and, 4th class - 26 to 40 fish/kg. Farm-gate price varies from LE. 7.85/kg 1st class tilapia to LE 1.75/kg 4th class tilapia. Greater yields of 1st and 2nd class tilapia were obtained where organic fertilization was used in combination with formulated feeds than where chemical fertilization alone or formulated feed alone were used. Results indicated that ponds stocked with young-of-year monosex tilapia and managed according to the tested systems were feasible in Egypt.

Yield Characteristics of Two Species of Tilapia under Two Different Pond Environments

Work Plan 7, Egypt Study 1B

Bartholomew W. Green
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA

Zeinab El Nagdy and Abdel R.E. Gamal
Central Laboratory for Aquaculture Research
Agricultural Research Center
Abbassa, Egypt

Abstract

PD/A CRSP research designs have been based on use of Nile tilapia (Oreochromis niloticus) as the test species because this species was common to all research sites. In Egypt, Nile and blue (O. aureus) tilapia, both good culture species, are endemic. The objective of this experiment was to compare production characteristics and production economics of O. niloticus and O. aureus reared in ponds managed under two different nutrient input regimes. Eighteen 0.1-ha ponds at the Central Laboratory for Aquaculture Research, Abbassa, Abou Hammad, Sharkia, Egypt, were used for this study using a completely randomized design in 3 x 2 factorial arrangement, where factors were tilapia species (Nile, blue, or co-stocked) and pond nutrient input regime (chemical fertilization or fertilization then feed). Weekly applications of nitrogen at 25 kg/ha and phosphorus to maintain an N:P ratio of 4:1 were made in the Chemical Fertilizer treatment. In the Fertilizer then Feed treatment, chicken litter was applied weekly at 1,000 kg dry matter/ha for the first eight weeks followed by feed (25% protein commercial fish feed) only. Ponds were stocked with sex-reversed tilapia fingerlings on 1 July 1994 at a stocking rate of 20,000 fingerlings/ha. Ponds are scheduled to be harvested after completion of 150 days of grow-out. Based on seine samples and estimated fish biomass, and assuming 20,000 fish/ha, the average mean individual fish weight after 83 days of growth was calculated. The highest estimated biomass and average weight were obtained in the Fertilizer then Feed treatment for O. niloticus 3,027 kg/ha and 151.4 g/fish, respectively. The co-stocked Chemical Fertilizer treatment resulted in the lowest average weight/fish (70.8) and in the lowest estimated biomass (1,415 kg/ha).

Nutrient Input Management by the Computer Program, PONDCLASS, and by Concentration of a Key Nutrient

Work Plan 7, Honduras Study 4A

David R. Teichert-Coddington
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA

Herbert Ramos
National Fish Culture Research Center
El Carao, Comayagua, Honduras

Abstract

Three simultaneous experiments were carried out to verify the pond management software PONDCLASS, to regulate pond fertilization by total ammonia concentration, and to evaluate the effect of raising the fish stocking rate from 2 to 3/m2. The control was equal in all studies; ponds were fertilized weekly with chicken litter at 250 kg dry matter/ha, urea to maintain weekly total nitrogen input at 28 kg/ha, and diammonium phosphate to supply 7 kg/ha total phosphorus input. Mean fish weight and production of the control treatment were 15% and 28% greater, respectively, than PONDCLASS means. Excessive nitrogen fertilization was recommended by PONDCLASS. Fish production was thought to be limited by primary productivity, which in turn was limited by carbon. The effectiveness of fertilizer input regulation by total ammonia was inconclusive because of poor treatment management. Increasing the tilapia stocking rate from 2 to 3/m2 had no significant affect on fish production or water quality. The mean average fish weight of the control treatment was 41% greater than the mean average weight of fish from the higher density treatment.

Management of Carbon Dioxide Balance for Stability of Total Alkalinity and Phytoplankton Stocks in Fertilized Fish Ponds

Work Plan 7, Thailand Study 6

James P. Szyper
Hawaii Institute of Marine Biology
University of Hawaii at Manoa
Kaneohe, Hawaii, USA

Kevin D. Hopkins
College of Agriculture
University of Hawaii at Hilo
Hilo, Hawaii, USA

Abstract

Stability of phytoplankton stocks and photosynthetic activity is important to successful pond culture. Large phytoplankton stocks in fertilized ponds can be unstable, and low total alkalinity (TA) can limit photosynthesis in ponds and contribute to instability. It is important to understand management of TA because it can change substantially during growth cycles in ponds, even when soils are conditioned. This experiment documented temporal trends of TA in 15 ponds, and quantified the effect of interim additions of soluble carbonate. For the CRSP Global Experiment, one of the five triplicated treatments consisted of inputs management using the PONDCLASS decision-support system software; another treatment consisted of regular inputs according to the specified control protocol of Work Plan 7.

The results of this experiment are currently undergoing analysis; results discussed here are preliminary. The five treatments produced no significant differences in final mean individual fish weights, survival, or net yields (P > 0.05, Single-factor ANOVA). Neither were there significant treatment differences in mean concentrations of chlorophyll a or daytime net primary production.

Management according to PONDCLASS produced yields with (numerically) greater efficiency than did treatments involving regular weekly fertilizer inputs in constant amounts, because similar yields were produced with less input. The net yields for all ponds, extrapolated to units of t/ha/y, ranged from 3.3 to 6.5. These are approximately double yields previously obtained at this site in the same season (wet) during earlier experiments, but are substantially less than yields obtained with these methods at a nearby site.

It is likely that rainfall affected the attempt to examine effects of soluble carbonate inputs. During the first 50 days, when no rain fell, alkalinity tended to decline during sampling intervals in all ponds, although concentrations were effectively stabilized in ponds receiving carbonate additions. After the first 50-day period the wet season began, and alkalinity showed little decline in ponds of any treatment. Daytime net primary production ranged (pond-by-pond) from -0.1 to 19.4 mg O2 l/d, with a mean of 7.0 for the experiment, equivalent to 2.0 g C/m/d. Higher values have been observed on this site, particularly during seasons without rain and/or cloud cover.

If completed analyses show that addition of soluble carbonate is effective in stabilizing TA, such inputs can readily be incorporated into the PONDCLASS and POND software systems and into transferred CRSP protocols. This will effectively eliminate the potential for decreasing alkalinity due to photosynthetically-mediated pH dynamics during production cycles in ponds, leading to more stable blooms and production rates, and thus to more reliable fish production protocols.